While H. glaciei is not the oldest bacteria to be resurrected—one sample collected in Tibet was brought back to life after 750,000 years—it is the first ancient "ultramicrobacteria" to be revived and characterized in detail, said study leader Jennifer Loveland-Curtze of Pennsylvania State University.

Survival of the Smallest

Ultramicrobacteria, tiny even by bacterial standards, are about 10 to 50 times smaller than the common human intestinal microbe E. coli.

Their diminutive size could give the bacteria a survival advantage over other microorganisms.

H. glaciei, for example, is thought to have survived in thin capillaries of nutrient-rich water in the Greenland glacier that would have been too tight a fit for larger bacteria.

Ultramicrobacteria may also be similar to the types of life that might be found in the icy environments of other worlds, such as the polar caps of Mars or the frozen sea of Jupiter's moon Europa, Loveland-Curtze said.

"If there had been life on these worlds, you might be able to find traces of it and potentially cultivate something from the ice," she added.

The research is detailed in the June issue of International Journal of Systematic and Evolutionary Microbiology.